High-energy radiation from the relativistic jet of Cygnus X-3

TL;DR

This paper models the high-energy gamma-ray emission from Cygnus X-3, suggesting it originates from electron-positron pairs accelerated in the jet, with implications for the system's geometry and the nature of its compact object.

Contribution

It introduces a scenario where gamma-ray emission is produced by pairs accelerated in the jet, providing insights into the jet orientation and the system's compact object.

Findings

Jet likely aligned close to the line of sight.

Pairs are not located within the system.

A massive compact object is favored.

Abstract

Cygnus X-3 is an accreting high-mass X-ray binary composed of a Wolf-Rayet star and an unknown compact object, possibly a black hole. The gamma-ray space telescope Fermi found definitive evidence that high-energy emission is produced in this system. We propose a scenario to explain the GeV gamma-ray emission in Cygnus X-3. In this model, energetic electron-positron pairs are accelerated at a specific location in the relativistic jet, possibly related to a recollimation shock, and upscatter the stellar photons to high energies. The comparison with Fermi observations shows that the jet should be inclined close to the line of sight and pairs should not be located within the system. Energetically speaking, a massive compact object is favored. We report also on our investigations of the gamma-ray absorption of GeV photons with the radiation emitted by a standard accretion disk in Cygnus X-3. This study shows that the gamma-ray source should not lie too close to the compact object.